JP2011066961A - Power generation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a generator which converts vibrating energy into electrical energy, especially, a compact and large output vibration drive type of capacitive generator which is manufactured using a MEMS technique. <P>SOLUTION: The generator has a dielectric G1, a movable part G4 which faces the dielectric with a specified distance from the dielectric G1, an electret G6 and a counter electrode G5, which generate a fringe fields to pierce the dielectric G1 between two electrodes, while being formed under the movable part G4. The generator outputs a charge introduced into the counter electrode G5 as a current, when the volume share of the dielectric G1 between the electret G6 and the counter electrode G5 changes according to the horizontal displacement of the movable member G4. The generator has a metal layer G2, which is formed on the surface of the dielectric G1 to prevent the fringe field from penetrating the dielectric G1 and a fluororesin layer G3, which is formed to cover the dielectric G1 and the metal layer G2 and have flat surfaces with respect to the movable member G4. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power generation device that converts kinetic energy (vibration energy) into electrical energy, and more particularly to a vibration-driven capacitive power generation device that is manufactured using MEMS [Micro Electromechanical System] technology.

  FIG. 54 is a schematic diagram showing a conventional example of a vibration power generation apparatus manufactured using the MEMS technology. The vibration type power generation device of this conventional example has a structure in which the upper unit U1 and the lower unit U2 are individually created using bulk MEMS technology and are bonded to each other.

  54, reference numeral 100 is Parylene [registered trademark], reference numeral 101 is a silicon substrate, reference numeral 102 is a silica layer, reference numeral 103 is an electret, reference numeral 104 is a counter electrode, reference numeral 105 is a base electrode, reference numeral 106 is Pyrex ( (Registered trademark) and reference numeral 107 denote spacers.

  The principle of operation of the vibration type power generation device having the above configuration is that the overlapping area between the electret 103 and the counter electrode 104 is changed by vibration in the biaxial plane direction (X direction, Y direction), and the charge induced to the counter electrode 104 is changed. The change was drawn out as current.

  In addition, as a related technique of the vibration power generation apparatus manufactured using the MEMS technique, for example, Patent Document 1 can be cited.

JP 2009-77614 A

  However, in the conventional vibration type power generation device, the generated power is about 10 μW, and its application is limited.

  In addition, since the above-described conventional vibration power generator has a structure in which the electret 103 and the counter electrode 104 face each other, if the gap distance between the upper unit U1 and the lower unit U2 is designed too small, the electret 103 There is a possibility that electrostatic attraction acts between the counter electrode 104 and the both electrodes come into contact with each other, or the injected charge of the electret 103 is discharged. For this reason, the gap distance between the upper unit U1 and the lower unit U2 must be designed to be large to some extent. However, in order to increase the capacity change due to vibrations after increasing the gap distance, it is opposed to the electret 103. It is necessary to design the area of the electrode 104 to be large, and as a result, it is necessary to further increase the gap distance. Due to such a vicious circle, the conventional vibration power generation apparatus is designed with, for example, a gap distance of about 70 μm and a lateral size of the electret 103 of about 150 μm, and there is room for further improvement in terms of downsizing the apparatus. It was.

  Further, in the above-described conventional vibration type power generation device, before the upper unit U1 and the lower unit U2 are bonded together, charge injection (charging) to the electret 103 is performed without contact using corona discharge (atmospheric discharge). It was done. However, in order to perform such a charge injection process, a large-scale corona discharge facility is required, which is disadvantageous in terms of manufacturing cost.

  In view of the above problems, an object of the present invention is to provide a small-sized and large-output power generator.

  In order to achieve the above object, a power generation device according to the present invention includes a dielectric, a movable part facing a predetermined distance from the dielectric, and formed on the dielectric side of the movable part. An electret that generates a fringe electric field so as to pass through the dielectric, and a counter electrode, and the volume occupancy ratio of the dielectric occupying between the electret and the counter electrode is horizontal to the movable body. A power generation device that outputs the electric charge introduced into the counter electrode as a current to the outside of the device when changed according to a displacement in a direction, formed on the movable part side surface of the dielectric, and the fringe electric field is A metal layer for preventing entry into the dielectric; and a fluororesin or a polyimide resin formed so as to cover the dielectric and the metal layer and having a horizontal surface with respect to the movable body Volatility good low dielectric insulating film (e.g., static friction coefficient of 0.5 or less and a specific dielectric constant of 4.0 or less); there is a comprising a structure (first structure).

  Note that in the power generation device having the first configuration, the metal layer may have a configuration (second configuration) in which the metal layer is formed to protrude on the movable portion side surface of the dielectric.

  In the power generation device having the first configuration, the metal layer may be configured to be buried and formed on a surface of the dielectric on the movable part side (third configuration).

  In order to achieve the above object, the power generation device according to the present invention includes a dielectric, a movable part facing the dielectric at a predetermined distance, and a dielectric-side surface of the movable part. An electret that generates a fringe electric field so as to penetrate the dielectric between the two electrodes, and a counter electrode; and a volume occupancy ratio of the dielectric that occupies between the electret and the counter electrode is the movable body When the electric power is changed according to the horizontal displacement of the power generation device, the electric charge introduced into the counter electrode is output as an electric current to the outside of the device, and the dielectric is formed on the surface of the movable part, A configuration (fourth configuration) is provided that includes a groove for preventing the fringe electric field from entering the dielectric.

  Note that the power generation device having the fourth configuration includes a low dielectric constant layer (relative dielectric constant of 100 or less) such as silica, which is laminated inside the groove and flattens the movable portion side surface of the dielectric. (5th configuration).

  Further, the power generation device having the fifth structure is formed so as to cover the dielectric and a low dielectric constant layer such as silica, and has a horizontal surface with respect to the movable body, such as a fluorine resin or a polyimide resin. It is preferable to adopt a configuration (sixth configuration) having a low dielectric insulating film with good slidability.

  Further, the power generation device having any one of the first to sixth configurations includes a beam portion having a length in the thickness direction larger than the length in the width direction as a support member of the movable portion (seventh). (Configuration).

  Further, in the power generation device having any one of the first to seventh configurations, the electret and the counter electrode are each formed in a comb-teeth shape having a plurality of comb-teeth portions, and are viewed from above in a plan view. It is preferable to adopt a configuration (eighth configuration) in which the comb teeth portions are alternately arranged at a predetermined interval.

  Further, the power generation device having any one of the first to eighth configurations includes an electret terminal (terminal from which the electret material is exposed) for injecting a predetermined amount of electric charge to the electret by contact discharge. (9th configuration).

  Further, in the power generation device having any one of the first to ninth configurations, the dielectric may have a configuration (tenth configuration) having a relative dielectric constant of 1,000 or more.

  Further, in the power generation device having any one of the first to tenth configurations, the gap region between the dielectric and the movable body is in a low vacuum state (a state that is not high vacuum or ultra vacuum) (first vacuum). 11 configuration).

  Further, in the power generation device having any one of the first to tenth configurations, a configuration (a twelfth configuration) may be adopted in which a gap region between the dielectric and the movable body is filled with a predetermined gas. .

  In the power generation device having the twelfth configuration, the predetermined gas may be any one of air, an inert gas, and a gas having a discharge preventing effect (a thirteenth configuration).

In the power generation device having the thirteenth configuration, the main component of the gas having the discharge preventing effect may be SF ₆ (fourteenth configuration).

  The power generation device having the fourteenth configuration may be configured to be manufactured using a surface micromachining technique (fifteenth configuration).

  According to the present invention, it is possible to provide a small-sized and large-output power generator.

Electrical model diagram of electrode-to-face power generator using ferroelectric PZT plate Schematic diagram for explaining the effect of splitting the electret into comb teeth (without comb teeth) Schematic diagram for explaining the effect of dividing the electret into comb teeth (with comb teeth) Schematic diagram for explaining the principle of power generation (initial position of movable body) Schematic diagram for explaining power generation principle (after horizontal movement of movable body) Schematic diagram for explaining power generation principle (after vertical movement of movable body) Simulation model diagram The figure which shows the capacity | capacitance change with respect to the displacement of a X direction (horizontal direction). The figure which shows the capacity | capacitance change with respect to the displacement of a Z direction (vertical direction). Schematic diagram conceptually showing the power generator corresponding to all XYZ directions Sectional drawing which shows the manufacturing process of an electric power generating apparatus (1st state) Sectional drawing which shows the manufacturing process of an electric power generating apparatus (2nd state) Sectional drawing which shows the manufacturing process of an electric power generating device (3rd state) Sectional drawing which shows the manufacturing process of an electric power generating apparatus (4th state) Sectional drawing which shows the manufacturing process of an electric power generating apparatus (5th state) Sectional drawing which shows the manufacturing process of an electric power generating apparatus (6th state) Equivalent circuit diagram of electrostatic discharge simulator Schematic diagram of CYTOP film discharge conditions (atmospheric discharge model) Schematic diagram of discharge conditions for CYTOP film (contact discharge model) The perspective view which showed the structure of the electric power generating apparatus by 1st Embodiment of this invention. Sectional view along line α1-α1 in FIG. The top view of the electric power generating apparatus by 1st Embodiment of this invention. The perspective view which showed the structure of the ferroelectric layer of the electric power generating apparatus by 1st Embodiment of this invention. The top view which looked at the proof mass of the electric power generating apparatus by 1st Embodiment of this invention from the back surface side Sectional view along line β1-β1 in FIG. The perspective view which showed a part of electric power generating apparatus by 1st Embodiment of this invention. Schematic sectional view for explaining the operation of the power generator according to the first embodiment of the present invention. Graph showing the relationship between the thickness of the ferroelectric layer and the coverage Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 1st Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 1st Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 1st Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 1st Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 1st Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 1st Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 1st Embodiment of this invention. The top view for demonstrating the manufacturing method of the electric power generating apparatus by 1st Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 1st Embodiment of this invention. The perspective view which showed the structure of the electric power generating apparatus by 2nd Embodiment of this invention. Sectional view along the line α2-α2 in FIG. The top view of the electric power generating apparatus by 2nd Embodiment of this invention. The perspective view which showed the structure of the ferroelectric layer of the electric power generating apparatus by 2nd Embodiment of this invention. The top view which looked at the proof mass of the electric power generating apparatus by 2nd Embodiment of this invention from the back surface side The perspective view which expanded and showed the structure of the beam part in the electric power generating apparatus by 2nd Embodiment of this invention. Sectional view taken along line β2-β2 in FIG. The perspective view for demonstrating operation | movement of the electric power generating apparatus by 2nd Embodiment of this invention. Graph showing the relationship between the thickness of the ferroelectric layer and the coverage Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 2nd Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 2nd Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 2nd Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 2nd Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 2nd Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 2nd Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 2nd Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 2nd Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 2nd Embodiment of this invention. The top view for demonstrating the manufacturing method of the electric power generating apparatus by 2nd Embodiment of this invention. Sectional drawing for demonstrating the manufacturing method of the electric power generating apparatus by 2nd Embodiment of this invention. The perspective view which showed the structure of the proof mass and beam part of the electric power generating apparatus by the 1st modification of this invention The top view which showed the structure of the electric power generating apparatus by the 2nd modification of this invention Sectional drawing which showed the structure of the electric power generating apparatus (metal layer protrusion type) by the 3rd modification of this invention Sectional drawing which showed the structure of the electric power generating apparatus (metal layer buried type) by the 3rd modification of this invention The schematic diagram for demonstrating the electric power generation principle of the electric power generating apparatus by the 4th modification of this invention (initial position of a movable body). Schematic for demonstrating the power generation principle of the power generator by the 4th modification of this invention (after horizontal movement of a movable body) Sectional drawing which showed the 1st structural example (trench type) of the electric power generating apparatus by the 4th modification of this invention. Sectional drawing which showed the 2nd structural example (silica laminated type) of the electric power generating apparatus by the 4th modification of this invention. Sectional drawing which showed the 3rd structural example (protective layer formation type) of the electric power generating apparatus by the 4th modification of this invention. Schematic diagram showing a conventional example of a vibration power generator manufactured using MEMS technology

  In the present specification, a vibration drive type power generator is proposed for the purpose of energy harvesting. In this power generator, electrets and counter electrodes arranged alternately are formed on the same surface at the lower part of the proof mass. The characteristics of the power generation device proposed in this specification are as follows. The first feature is that a fringe electric field formed on a ferroelectric substrate is used. The second feature is that a change in volume occupancy of the dielectric occupying between the two electrodes is used. A third feature is that a ferroelectric having a large relative dielectric constant of 1,000 or more is used as a substrate, not as a movable body. The fourth feature is that it is expected to obtain a larger change in capacitance value than the conventional method with respect to the amount of movement of the proof mass. The fifth feature is that since surface micromachining can be applied, it is possible to simplify the structure including the wiring and reduce the manufacturing cost. In this specification, in order to confirm the validity of the proposed operating principle, calculation of electric field and investigation of capacitance change are performed. However, for these calculation and investigation, a finite element method (FEM [FEM [ Finite Element Method]) simulation is used. The MEMS manufacturing process is designed for a power generation system formed by three devices each corresponding to a multi-axis direction (X-axis direction, Y-axis direction, and Z-axis direction). As a first step in manufacturing the device, a predetermined amount of electric charge is successfully injected into the polymer film (CYTOP [registered trademark] film) formed in a comb shape.

(Section 1-Introduction)
In recent years, micro power generation systems have attracted much attention for applications such as batteries and thrusters. As a battery for low power consumption applications such as ubiquitous sensor networks and mobile communications, vibration-driven power generators have been reported. Compared to the electromagnetic type and the piezoelectric type, the electrostatic power generation device is considered to be advantageous in terms of compatibility with the microfabrication technology and compatibility with low frequency band vibrations of several tens of Hz or less. Regarding the micro-machined capacitive vibration-driven power generator, some research results regarding its power generation capacity have been reported. In such a vibration drive type power generator, an electret is used. An electret is an element that retains the charge injected therein for a long period, that is, semipermanently. Also in this specification, capacitive MEMS power generation devices using electrets are dealt with with emphasis.

In the reported capacitive power generation device, a gas such as air or vacuum (relative permittivity ε = 1) is used as an insulator between two electrodes. If the above insulator is replaced with a ferroelectric material, for example, PZT or BaTiO ₃ having a relative permittivity ε much larger than that of the above insulator (the relative permittivity ε is usually 1,000 or more). It can be expected to obtain a larger power output. In addition, the reported capacitive power generation apparatus normally uses unidirectional vibration. In order to collect kinetic energy due to random human body movements, a power generator using multi-axis vibration is more desirable.

  In view of these circumstances, the inventors of the present application aim to develop an electret power generation system that responds to a change in capacity caused by the movement of the proof mass. This electret power generation system has the following two features. The first feature is that the power generation device described above can generate a current not only from vibration in the horizontal direction but also from vibration in the vertical direction. This is useful for improving the efficiency of energy recovery. The second feature is that the above power generation apparatus not only uses the change in the overlap area and / or gap distance between the two electrodes, but also uses the change in the volume occupancy of the dielectric material between the two electrodes. It is a point.

In order to achieve the latter purpose, the inventor of the present application previously used a ferroelectric PZT (relative permittivity ε _r = 2600) as a proof mass for the purpose of obtaining a very large capacitance change. Reported device. The principle of this electret power generator is schematically shown in FIG. FIG. 1 is an electrical model diagram of an electrode-facing power generation device using a ferroelectric PZT plate. In the figure, symbol A1 indicates a base electrode, symbol A2 indicates an electret, symbol A3 indicates parylene, symbol A4 indicates a PZT plate, and symbol A5 indicates a counter electrode. Since a predetermined amount of charge Q is trapped in the electret A2 on the base electrode A1 from the beginning, if the capacitance value C changes between the two electrodes (between the electret A2 and the counter electrode A5), the charge Q Is induced to the counter electrode A5, and the current I is supplied to the external circuit. The capacitance value C is expressed by the following equation (1).

In the above equation (1), ε ₀ is the relative dielectric constant of air, S is the overlapping area between the two electrodes facing each other, and d is the gap distance between the two electrodes. When the proof mass is driven to vibrate in the horizontal direction, the overlap area S changes and the capacitance value C changes by ΔC. It should be noted that since the overlapping area S multiplied by the relative dielectric constant ε _r affects the capacitance value C, the larger the relative dielectric constant ε _r , the larger the amount of change ΔC can be obtained. On the other hand, when the proof mass is driven to vibrate in the vertical direction, the gap distance d changes, and the capacitance value C changes by ΔC. Also in this case, for the same reason as described above, it is more preferable that the relative dielectric constant ε _r is large.

  However, the reported power generator described above has one problem. In the conventional capacitive power generation device including this power generation device, as shown in FIGS. 2A and 2B (schematic diagram for explaining the effect of dividing the electret into comb-shaped members), the proof mass is moved horizontally. In order to increase the amount of change ΔC in the capacitance value C, the electret A2 should be divided into comb-shaped members. This is because the change in the overlapping area ratio is b / a in the configuration of FIG. 2A, whereas 2n × (b / a) (where n is the number of comb teeth) in the configuration of FIG. 2B. This is because the area ratio changes n times as much as the same amount of horizontal movement.

  At this time, in order to maximize the overlapping area S between the two electrodes for the purpose of increasing the amount of power generation, it is required to accurately arrange the comb-shaped electret A2 and the corresponding comb-shaped counter electrode A5. Is done. Conventional capacitive power generators generally comprise a member that supports electret A2 and a member that supports counter electrode A5, and these members are individually manufactured and then face each other with a small gap distance. It was finally pasted in the form. However, in such an assembly structure, it is extremely difficult to accurately arrange the electret A2 and the counter electrode A5.

In order to solve such a problem, a capacitive power generation device capable of surface micromachining is proposed in this specification. And as shown to FIG. 3A-FIG. 3C, in this electric power generating apparatus, the comb-shaped electret B2 and the counter electrode B4 are formed in the same surface in the lower part of the proof mass B1. The alignment here is accurately performed using a single mask by photolithography technology. Also, electrical wiring is necessary only on the surface of the proof mass B1, and is not necessary on the surface of the substrate B5. Therefore, it can be expected to simplify the structure and reduce the manufacturing cost. Further, in this power generator, the proof mass B1 is provided on an upper portion of a ferroelectric substrate B5 such as a bulk PZT or BaTiO ₃ screen-printed on a ceramic substrate. Ferroelectric materials are generally difficult to etch. Therefore, in the power generation apparatus proposed this time, a ferroelectric material is used as the substrate B5 instead of the suspended proof mass B1 in view of an actual manufacturing process. Such a configuration is one of the features of the power generator proposed here. The fringe electric field B7 formed on the ferroelectric substrate B5 is effectively used. The detailed principle will be described later.

  The original features of the power generator proposed this time can be summarized as follows. The first feature is that a fringe electric field formed between two alternately arranged electrodes (that is, an electret and a counter electrode) is used. The second feature is that a change in volume occupancy of the dielectric occupying between the two electrodes is used. The third feature is that a ferroelectric having a large relative dielectric constant of 1,000 or more is used as a substrate, not as a proof mass. The fourth feature is that these devices are expected to obtain a larger change in capacity value than the prior art with respect to the amount of movement of the proof mass, and thus a larger amount of power generation can be obtained. The fifth feature is that since surface micromachining can be applied, it is possible to simplify the structure including the wiring and reduce the manufacturing cost.

  Further, the contents of the present specification described below are organized as follows. The next section 2 explains the concept and operating principle of the power generation apparatus proposed this time. In Section 3, a finite element method (FEM) simulation is performed to calculate the electric field and investigate the capacitance change. Section 4 describes the manufacturing process of the power generator. In Section 5, a predetermined amount of charge is pre-injected into the polymer CYTOP film before the actual production of the power generator. This is to confirm the possibility of producing electrets using research equipment.

(Section 2-Concept and Principle of Operation)
2.1 Device Structure In this section, the concept and operation principle will be described with reference to FIGS. 3A to 3C. 3A to 3C are schematic diagrams for explaining the principle of power generation. The movable body is in the initial position, the movable body is horizontally moved, and the movable body is moved vertically. The state after being done is shown. In this figure, symbol B1 is a proof mass (movable body), symbol B2 is an electret, symbol B3 is a base electrode, symbol B4 is a counter electrode, symbol B5 is a ferroelectric substrate, symbol B6 is a floating electrode, and symbol B7 indicates a fringe electric field.

  The electret B2 is formed of a polymer material (for example, CYTOP is used in this embodiment) formed adjacent to the electrically grounded base electrode B3. As shown in FIGS. 3A to 3C, the comb-shaped electret B2 is formed on the lower surface of the movable body B1 made of an insulator (in the present embodiment, for example, SU-8 or parylene is used). The comb-shaped counter electrode B4 is formed on the lower surface of the movable body B1, as with the electret B2. That is, two electrodes (namely, electret B2 and counter electrode B4) arranged alternately are formed on the lower surface of the movable body B1. A fringe electric field B7 is formed between the two electrodes. By using the fringe electric field B7, it is possible to apply surface micromachining more preferable in terms of manufacturing and cost.

By using the MEMS technique, the movable body B1 is formed on a PZT plate or a ferroelectric substrate B5 such as BaTiO ₃ on a ceramic plate. Here, it is known that the lines of electric force penetrate the dielectric, but do not penetrate the conductor. Therefore, a comb-like metallic floating electrode B6 is formed on the surface of the ferroelectric substrate B5. Note that the metallic floating electrode B6 formed on the surface of the ferroelectric substrate B5 is in an electrically floating state, that is, not connected to a ground terminal, a power supply terminal, or the like.

2.2 Principle of operation during horizontal vibration When the movable body B1 is moved in the horizontal direction by external vibration input, as shown in comparison with FIGS. 3A and 3B, the fringe electric field B7 and the floating electrode The relative arrangement relationship with B6 changes, and the state of the lines of electric force passing through the ferroelectric substrate B5 changes. That is, at the initial position of the movable body B1 (see FIG. 3A), the lines of electric force are likely to enter the ferroelectric substrate B5, but the position after the horizontal movement of the movable body B1 (FIG. 3B). )), The electric lines of force are blocked by the floating electrode B6, which makes it difficult to enter the ferroelectric substrate B5. This fact means that the capacitance C (= ε _r ε ₀ S / d, see section 1 for the meaning of the sign) formed between the electret B2 and the counter electrode B4 changes. This change is caused by a change in the volume ratio between the dielectric and air existing between the two electrodes, that is, the equivalent relative dielectric constant ε _r .

  Along with the change in capacitance between the two electrodes, a predetermined amount of charge Q is introduced into the counter electrode B4. And this electric charge Q is drawn out as the electric current I based on the following (2) Formula.

The above (2) where, V _charge indicates the surface voltage of the electret B2. On the left side of FIGS. 3A and 3B, an equivalent circuit schematically showing the concept and operating principle of the power generation apparatus proposed this time is depicted.

As can be seen from the above equation (2), it should be noted that the larger the relative dielectric constant ε _r is, the better, in generating the large current I. The above equation (2) shows the importance of adopting a material having a high dielectric constant, that is, a ferroelectric, as a material for forming the substrate B5.

2.3 Operating Principle during Vertical Vibration When the movable body B1 is moved in the vertical direction, the vertical distance between the movable body B1 and the substrate B5 is greater as shown in comparison with FIGS. 3A and 3C. When it becomes smaller, the equivalent relative dielectric constant ε _r becomes larger. Conversely, when the vertical distance between the movable body B1 and the substrate B5 becomes larger, the equivalent relative dielectric constant ε _r becomes smaller. Therefore, it is possible to generate power based on the same principle as that in the horizontal vibration.

(Section 3-FEM simulation on capacitance change)
3.1 Simulation conditions In this section, the above operating principle is theoretically confirmed. It is difficult to calculate the fringe electric field analytically. Therefore, in order to know the relationship between the change in capacity and the amount of movement of the proof mass, an FEM simulation was performed. As FEM software, Comsol FEMLAB was employed. The simulation conditions are shown in FIG. 4 is the same as that in FIGS. 3A to 3C, B1 is a proof mass (material: parylene (ε _r = 3.15), B2 is an electret (material: CYTOP (ε _r = 2.1), surface voltage: -300 V), B3 is a base electrode (0 V), B4 is a counter electrode (0 V), B5 is a substrate (material: PZT (ε _r = 2600), or SiO ₂ (ε _r = 3.1)), symbol B6 is a floating electrode, symbol B8 is air existing between the gaps, as shown in FIG. Taking into account, a two-dimensional (2D) model was adopted, and the specific manufacturing process designed for the actual power generator (details are detailed in Section 4) for the structure, material, and dimensions. Refers to.

In order to investigate the effect of using a ferroelectric as a substrate, as a material of the substrate B5, in addition to PZT (ε _r = 2,600), SiO ₂ (ε _r = 3.1) is used for reference. Using.

  The total capacity of the analysis space is calculated by integrating the electrical data of all the FEM elements listed in the following equation (3).

Above (see assumed value is -300 V, Section 5) (3) where, W _e is the total amount of electrical energy, V _charge is the surface voltage of the electret B2. E indicates an electric field, and D indicates an electrical displacement amount. By using the parameter values in the analysis space, the total capacity of a 1 mm × 1 mm plate is calculated.

3.2 Simulation Result From the simulation result regarding the electric field lines and the distribution of the electric potential, it is confirmed that the electric field lines are surely entering the ferroelectric substrate B5 while being partially blocked by the floating electrode B6. I was able to.

  Further, the displacement C of the proof mass B1 provides the capacitance C according to the above-described equation (1). FIG. 4 shows a simulation result of the change in capacitance according to the mass displacement in the horizontal direction (X direction) from the initial position (see FIG. 3A). Similarly, FIG. 5 shows a simulation result relating to a mass change in the vertical direction (Z direction), that is, a capacitance change according to a gap distance between the movable body B1 and the surface of the substrate B5.

By looking at these figures, it is proved that the capacity is surely changed regardless of the mass displacement in either the horizontal direction or the vertical direction. This is effective in generating power in response to multi-axis vibration input. Further, it is proved that the capacity change rate corresponding to the mass displacement when the PZT substrate is used is superior to that when SiO ₂ is used. This indicates that the use of a ferroelectric substrate having a large relative dielectric constant is effective.

(Section 4-Manufacturing Process)
An overview of the MEMS power generation system is shown in FIG. In addition, the MEMS power generation system shown in this figure includes three power generation devices C1, C2, and C3 for the X, Y, and Z directions. Further, in the figure, reference numeral D1 indicates a proof mass (movable body), reference numeral D2 indicates a beam portion, reference numeral D3 indicates an electret, reference numeral D4 indicates a counter electrode, and reference numeral D5 indicates a floating electrode.

  The manufacturing process of the power generation apparatus proposed this time is designed for an actual power generation apparatus and is shown in FIGS. 8A to 8F. In this section, the details are described below.

  FIG. 8A shows how aluminum sputtering and patterning is performed to form a floating electrode.

First, a silicon wafer E1 (thickness: 500 μm) is prepared. A surface-polished PZT plate E3 (10 mm square, thickness 100 μm, manufactured by Furuuchi Chemical Co., ε _r = 2600) is pasted on the silicon wafer E1. At this time, polydimethylsiloxane (PDMS [polydimethylsilozane]) is used as the adhesive E2. Thereafter, aluminum E4 (thickness: 0.1 μm) is sputtered on the surface of the PZT plate E3, and the comb-shaped floating electrode is patterned.

  FIG. 8B shows a state in which amorphous silicon is deposited by plasma enhanced chemical vapor deposition (PECVD) and slots and dimples are formed in the amorphous silicon.

Amorphous silicon E5 (thickness 1 μm) is deposited as a sacrificial layer using PECVD. Thereafter, in order to form slots E6 and dimples E7, etching is performed using SF ₆ plasma. The function of the amorphous silicon E5 will be described later.

FIG. 8C shows how CYTOP is spin-coated after parylene is deposited to protect the injected charge, and then the CYTOP is etched by O ₂ plasma.

  Parylene E8 (thickness: 2 μm) is deposited by CVD for the purpose of protecting the injected charge of the electret from being discharged during subsequent processes and when the movable body collides with the substrate. The Since the deposition of parylene E8 is equiangular, slot E6 (see also FIG. 8B) on amorphous silicon E5 is filled with parylene E8, thereby forming an anchor connecting the movable body and the substrate. Is done. In view of the mechanical strength of the connecting member connecting the beam portion and the anchor portion / mass portion, it is desirable that the height of the parylene E8 in both the anchor portion and the mass portion is the same. Therefore, the slot E6 is formed in the amorphous silicon E5, and the anchor contact area is minimized. The dimples E7 (see also FIG. 8B) formed on the amorphous silicon E5 are filled with the parylene E8, and after removing the amorphous silicon E5, bumps for preventing stiction (adhesion). Is formed.

CYTOP film E9 (Asahi Glass Co., Ltd., CTL-809 type) is spin coated on the surface of Parylene E8 and then dried at 120 ° C. for 10 minutes. A thickness of 0.3 μm can be obtained by one spin coating. This process is repeated 10 times for a total thickness of 3 μm. Finally, it is dried at 180 ° C. for 1 hour. The CYTOP film E9 is etched with O ₂ plasma to form a comb-shaped electret region.

  FIG. 8D shows how aluminum is sputtered and patterned to form the counter electrode. The charge injection into the CYTOP film by corona discharge (atmospheric discharge) is performed at this point.

Aluminum E10 (thickness 0.5 μm) is sputtered and patterned to form a comb-like counter electrode. Thereafter, a predetermined amount of charge is injected by corona discharge (atmospheric discharge) into the formed CYTOP film E9 (see also FIG. 8C) (details will be described later in Section 5). The assumed value of the surface voltage V _charge is −300V.

  FIG. 8E shows a state in which parylene is further deposited after parylene is deposited and aluminum as a base electrode is sputtered thereon.

  Parylene E11 (thickness 4 μm) is deposited to prevent discharge. Aluminum E12 (thickness 0.5 μm) is sputtered and patterned to form comb-teeth electret substrate electrodes. Again, Parylene E13 (thickness 3 μm) is deposited to prevent discharge.

FIG. 8F shows that after the SU-8 layer is spin-coated and patterned, parylene is etched by O ₂ plasma, and amorphous silicon is etched by XeF _2, so that the proof mass portion and the beam portion are dielectric. The state of being separated from the substrate is shown.

The SU-8 layer E14 (thick photoresist, manufactured by KAYAKU MICROCHEM, KMPR-1035) is spin coated and patterned to form a proof mass. Thereafter, parylene E13, E11, and E8 (see also FIGS. 8E and 8B) are etched by O ₂ plasma to form the support beam. Finally, sacrificial amorphous silicon E5 (see also FIG. 8B) is removed using XeF ₂ gas to separate the mass and beam from the dielectric substrate. This dry etching process is effective in preventing stiction. In order to efficiently generate power from human movements (vibrations of several tens of Hz), the aspect ratio (vertical / horizontal) is increased as a material for forming the beam part (spring part) that points to the proof mass part. Need to design. Therefore, in FIG. 8F, the SU-8 layer E14, which is easy to form a thick film, is adopted as the material of the beam portion.

  Currently, some of these processes are actually implemented, and optimum process conditions are being sought. The actual production and evaluation of power generators is for further study.

(Section 5-Charge Injection Test)
In this section, a preliminary experiment is performed in which a predetermined amount of charge is injected into the CYTOP film. Of course, other studies have already confirmed that charges can be injected into CYTOP films. Therefore, the result described here is a kind of follow-up study to confirm the charging capability of the devices currently available in our laboratory.

First, a silicon wafer is prepared. Parylene (thickness: 2 μm) is deposited on the surface of the wafer as an insulator for preventing discharge. A CYTOP film (thickness 3 μm) is then formed thereon (see section 4 for details). The CYTOP film is etched with O ₂ plasma to form a 5 μm-5 μm line-space pattern that becomes a comb-shaped electret.

  A predetermined amount of charge is injected into the processed CYTOP film by corona discharge. For this purpose, an electrostatic discharge simulator (type ESS-2002, manufactured by Noise Laboratories) is used. In this experiment, −8 kV is adopted as the output voltage of the discharge gun. The equivalent electrical circuit is shown schematically in FIG. In the experiment, two discharge models are applied. One is an atmospheric discharge model (see FIG. 10A), and the other is a contact discharge model (see FIG. 10B). Discharges were performed a total of 600 times with an interval of 0.5 seconds between each discharge. In contact discharge, the sample was kept in an insulated state by opening the switch during the discharge period.

  10A and 10B, reference numeral F1 indicates a silicon wafer, reference numeral F2 indicates parylene, reference numeral F3 indicates a CYTOP film, reference numeral F4 indicates a discharge simulator, and reference numeral F5 indicates a switch.

  After the discharge, the surface voltage of the CYTOP film was measured using an electrostatic sensor (type EF-S1 manufactured by SUNX). As a result, it was confirmed that about -350V was obtained in the atmospheric discharge model and -250V was obtained in the contact discharge model. By using an electrostatic discharge simulator, charge injection into the CYTOP film is certainly possible, and it was proved that the atmospheric discharge model is preferable to the contact discharge model from the viewpoint of obtaining a high surface voltage. However, other studies have reported higher surface voltages of about -1,000V. Research to catch up to this value by changing the experimental conditions of discharge, such as heating the substrate during discharge, is a future challenge.

(Section 6-Conclusion)
As described above, a capacitive power generation device capable of surface micromachining is proposed in this specification for the purpose of energy harvesting. In the power generator, electrets and counter electrodes arranged alternately are provided on the same surface in the lower part of the proof mass. This power generation device uses a fringe electric field formed in a ferroelectric substrate having a large relative dielectric constant of 1,000 or more.

  A finite element method (FEM) simulation was performed to investigate the change in capacitance according to the calculation of the electric field and the change in mass. As a result, the validity of the proposed operating principle was confirmed. The MEMS manufacturing process is designed for a power generation system formed by three devices each corresponding to multi-axis vibration (X-axis direction, Y-axis direction, and Z-axis direction).

  The overall production and evaluation of the actual power generation device is for further study. In particular, ascertaining the ability of a parylene film used as a protective layer for preventing discharge during a manufacturing process such as metal deposition or wet etching is an important issue to be preferentially studied.

  Energy harvesting using the above power generation device frees you from worrying about battery life.

  Further, by applying the above power generation device as a power source for various sensors and wireless devices (for example, a ZigBee / 300 MHz band specific low-power wireless device), a ubiquitous environment by a wireless sensor network can be constructed. That is, since various types of sensors and wireless devices need no power supply wiring, it is possible to realize information linkage in the network by distributing each device.

  In addition, the usage scenes of the ubiquitous environment using the power generation device include, for example, the medical / health field (health management and safety confirmation), structure monitoring (monitoring of wire breakage and bolt loosening), plant monitoring (monitoring of equipment abnormality) ), And distribution management (monitoring of distribution status and quality).

  Note that since the power generation device proposed in this specification can be applied with surface micromachining, the manufacturing cost can be reduced.

  Also, with the power generation device proposed in this specification, the gap distance between the substrate and the proof mass (movable body) can be reduced, so that a smaller size and higher efficiency than the conventional structure can be realized. It becomes possible.

  In addition, since the power generation device proposed in this specification can use a fringe electric field and a ferroelectric substance and an equivalent change in relative permittivity can be used for a power generation operation, the conventional structure (electret and The power generation efficiency (vibration detection sensitivity) can be significantly increased as compared with the structure in which the change in the overlapping area with the counter electrode is used for the power generation operation.

  Further, with the power generation device proposed in this specification, not only horizontal vibrations but also vertical vibrations can be used for power generation operation, so that further improvement in power generation efficiency can be realized. Become.

  In the above, two types of corona discharge (atmospheric discharge) and contact discharge have been studied as methods for injecting electric charge into the electret. If the power generator proposed in this specification is used, the electret is used. By pulling out a terminal from which the material is exposed (hereinafter, referred to as an electret terminal as appropriate) to the outside of the apparatus, it is possible to inject an electric charge into the electret using contact discharge in the final step of the manufacturing process. Therefore, since a large-scale corona discharge facility is not required, the manufacturing cost can be reduced. In addition, there is a merit that there is no worry about electric discharge during the manufacturing process. Also, since the discharge probe can be inserted from the through hole provided in the movable body and the charge can be injected into the CYTOP immediately before the sacrificial layer etching in the final step, surface micromachining is different from the conventional method in which the substrates are bonded. Applicable. Moreover, it leads to the elimination of misalignment between the comb-tooth electrode (electret and counter electrode) below the movable body and the floating electrode above the dielectric.

  As described above, the power generation device proposed in the present specification can realize 100 times higher output and 1/2 cost than the conventional power generation device.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 11 is a perspective view showing the structure of the power generator according to the first embodiment of the present invention. FIG. 12 is a cross-sectional view taken along the line α1-α1 in FIG. FIG. 13 is a plan view of the power generator according to the first embodiment of the present invention shown in FIG. 14-17 is a figure for demonstrating the structure of the electric power generating apparatus by 1st Embodiment of this invention. First, the structure of the power generation apparatus 50 according to the first embodiment of the present invention will be described with reference to FIGS.

  As shown in FIG. 11, the power generation device 50 according to the first embodiment includes a ceramic substrate 1, a ferroelectric layer 2 formed on the ceramic substrate 1, and the ceramic substrate 1 so as to surround the ferroelectric layer 2. And a proof mass 4 disposed inside the frame body portion 3. The ferroelectric layer 2 is an example of the “dielectric layer” in the present invention, and the proof mass 4 is an example of the “movable part” in the present invention.

The ceramic substrate 1 is made of Al ₂ O ₃ and has a thickness of about 1 mm. A glaze layer 5 is formed on the upper surface of the ceramic substrate 1. The glaze layer 5 is provided to obtain a smooth surface suitable for forming the ferroelectric layer 2 and the like. In addition, a wiring layer 6 formed by a screen printing method is provided on the upper surface of the ceramic substrate 1 (the glaze layer 5) and in a predetermined region outside the frame body portion 3. The wiring layer 6 is made of, for example, Au (gold).

Here, in the first embodiment, the ferroelectric layer 2 is made of BaTiO ₃ (relative dielectric constant: 1,000 or more). Further, as shown in FIGS. 12 and 14, the ferroelectric layer 2 is formed in a predetermined region on the ceramic substrate 1 (glaze layer 5) by a screen printing method. The ferroelectric layer 2 has a substantially quadrangular shape when seen in a plan view.

  In the first embodiment, the ferroelectric layer 2 is configured to have a thickness of 5 μm or more. Specifically, the ferroelectric layer 2 is configured to have a thickness t1 (see FIG. 16) of 5 μm to 20 μm.

  Further, the proof mass 4 is made of parylene (Parylylene resin) and has a thickness t2 (see FIG. 16) of about 5 μm as shown in FIGS. Further, as shown in FIG. 13, the proof mass 4 is formed in a substantially quadrangular shape (the length of one side is about 1000 μm) when seen in a plan view.

  Here, in the first embodiment, as shown in FIG. 15, two electrodes (first electrode 7 and second electrode 8) are adjacent to each other in the same plane on the back surface side (lower surface side) of the proof mass 4. It is formed to fit. Specifically, the first electrode 7 and the second electrode 8 are each formed in a comb-like shape in plan view, and the comb-tooth portion 7a of the first electrode 7 and the comb of the second electrode 8 are formed. It is comprised so that the tooth part 8a may be arranged by turns. Further, as shown in FIGS. 16 and 17, the width w of the comb tooth portion 7a of the first electrode 7 and the width w of the comb tooth portion 8a of the second electrode 8 are each configured to be about 5 μm, The length g from the comb tooth portion 7a of the first electrode 7 to the comb tooth portion 8a of the adjacent second electrode 8 is also configured to be about 5 μm. In the power generation device 50 according to the first embodiment, as shown in FIG. 15, the first electrode 7 and the second electrode 8 are formed on almost the entire back surface (lower surface) side of the proof mass 4.

  Said 1st electrode 7 is corresponded to a counter electrode, and consists of metal materials, such as aluminum (refer code | symbol B4 of FIG. 3A-3C and FIG. 4, and code | symbol E10 of FIG. 8D). The second electrode 8 includes an electret part (such as a CYTOP film) that holds a predetermined amount of charge semipermanently and a base electrode part (such as aluminum) that serves as a reference for potential during power generation. (See reference numerals B2 and B3 in FIGS. 3A to 3C and FIG. 4, reference numeral E9 in FIG. 8C, and reference numeral E12 in FIG. 8E).

  The proof mass 4 includes four beam portions 9 that are integrally connected as shown in FIGS. 11 and 13. The four beam portions 9 are arranged one by one at each of the four corner portions of the proof mass 4, and are formed so as to spread radially when viewed in a plan view. Further, the end portions of the four beam portions 9 are integrally connected to the frame body portion 3, respectively. Thus, the proof mass 4 is supported above the ferroelectric layer 2 in a state of being disposed so as to face the ferroelectric layer 2 as shown in FIGS. 11 and 12. A distance d (see FIGS. 12 and 16) from the upper surface of the ferroelectric layer 2 to the proof mass 4 (first electrode 7 and second electrode 8) is about 1 μm.

  Each of the four beam portions 9 has a thickness of about 5 μm and a width of about 50 μm. That is, the four beam portions 9 are configured such that the length in the width direction is larger than the length in the thickness direction so that the four beam portions 9 are easily elastically deformed in the vertical direction (arrow Z direction) with respect to the upper surface of the ceramic substrate 1. . Accordingly, the proof mass 4 supported by the four beam portions 9 is configured to be able to move in the vertical direction (arrow Z direction) with respect to the upper surface of the ceramic substrate 1 by the inertia force when acceleration is applied. Has been.

  In addition, the first electrode 7 described above is electrically connected to the pad electrode 7c through the connecting portion 7b as shown in FIG. On the other hand, of the second electrode 8 described above, the electret part that holds a predetermined amount of charge semi-permanently is in an electrically insulated state, and is a base electrode part for taking a potential reference during power generation Are electrically connected to the pad electrode 8c through the connection portion 8b. The pad electrode 7c is an electrode for extracting a current obtained by power generation, and is connected to a load that is a current supply destination when the power generation device 50 is used. On the other hand, the pad electrode 8c is an electrode for taking a potential reference during power generation, and is connected to a predetermined reference potential when the power generation apparatus 50 is used. Although not explicitly shown in the drawing, the power generation device 50 of the present embodiment applies a predetermined amount of electric charge to the electret portion of the second electrode 8 by contact discharge in the manufacturing process (final stage) of the power generation device 50. An electret terminal for injection is provided. The electret terminal is connected to a predetermined contact type discharge device (high voltage application device) at the time of the above charge injection, and is opened or grounded when the power generation device 50 is used.

  Further, the frame body portion 3 has a thickness larger than that of the proof mass 4 as shown in FIG. 12, and holds the proof mass 4 via the beam portion 9 as shown in FIGS. It has a function to do. In addition, the frame part 3 is mainly comprised from parylene. Further, an opening 3a for exposing the surfaces of the pad electrodes 7c and 8c is formed in a predetermined region of the frame 3.

  FIG. 18 is a schematic cross-sectional view for explaining the operation of the power generation device according to the first embodiment of the present invention. Next, with reference to FIGS. 15-18, operation | movement of the electric power generating apparatus 50 by 1st Embodiment of this invention is demonstrated.

  In the power generator 50 according to the first embodiment, as shown in FIGS. 16 and 17, a fringe electric field (a side between the electrodes) is formed between the comb teeth 7 a of the first electrode 7 and the comb teeth 8 a of the second electrode 8. 10) is generated. Here, as shown in FIG. 15, the first electrode 7 and the second electrode 8 that generate the fringe electric field 10 are each formed in a comb-like shape, and the comb-tooth portions 7a and 8a are alternately arranged. Therefore, the fringe electric field 10 is uniformly generated on almost the entire back surface (lower surface) side of the proof mass 4. On the other hand, as shown in FIGS. 16 to 18, the ferroelectric layer 2 facing the proof mass 4 is in a state of being disposed in the generated fringe electric field 10.

  When vibration in the vertical direction (Z direction) is applied to the power generation device 50 from this state, an inertial force acts on the proof mass 4, thereby moving the proof mass 4 in the arrow Z direction as shown in FIG. 18. For this reason, since the proportion of the volume of the ferroelectric layer 2 in the fringe electric field 10 changes, the capacitance value of the capacitor formed between the two electrodes changes. Along with the capacitance change, a predetermined amount of charge is introduced into the first electrode 7 (counter electrode), and this is output as a current.

  Next, the result of the computer simulation performed to confirm the effect of the power generation device 50 according to the first embodiment will be described. In this computer simulation, the coverage was obtained when the thickness t1 of the ferroelectric layer 2 was variously changed.

  FIG. 19 is a graph showing the relationship between the thickness of the ferroelectric layer 2 and the coverage. The vertical axis in FIG. 19 indicates the cover ratio (%), and the horizontal axis in FIG. 19 indicates the thickness t1 (μm) of the ferroelectric layer 2. That is, FIG. 19 shows the change in the cover ratio when the thickness t1 of the ferroelectric layer 2 is variously changed in the configuration of the power generation device 50 according to the first embodiment. Here, the coverage is expressed by the following equation (4).

  In the above equation (4), X1 indicates the number of electric lines of force of the fringe electric field 10 entering the region of the ferroelectric layer 2, and X2 cannot be turned in the region of the ferroelectric layer 2 and is strong. The number of lines of electric force that emerge from the lower part of the region of the dielectric layer 2 is shown.

  That is, the coverage is a numerical value indicating how much of the electric lines of force that enter the ferroelectric layer 2 are turning in the region in the ferroelectric layer 2. The higher this value, the greater the change in capacitance value corresponding to the displacement of the proof mass 4. Note that one of the voltages applied to the electrodes was 0 V (first electrode 7 or second electrode 8), and the other was 5 V (second electrode 8 or first electrode 7).

  As shown in FIG. 19, it was found that a coverage of 99% or more can be obtained by configuring the thickness t1 of the ferroelectric layer 2 to be 5 μm or more. Further, when the thickness t1 of the ferroelectric layer 2 is configured to be 10 μm or more, a cover ratio of almost 100% (99.8% or more) is obtained, and when the thickness t1 is configured to be 20 μm or more, a 100% cover is obtained. The rate was found to be obtained. When the thickness t1 of the ferroelectric layer 2 is 10 μm, the thickness t1 of the ferroelectric layer 2 is the width w of one comb tooth portion 7a (or 8a) of the first electrode 7 and the second electrode 8. (About 5 μm) and the total length (w + g: about 10 μm) of the length g (about 5 μm) from the comb tooth portion 7a of the first electrode 7 to the comb tooth portion 8a of the adjacent second electrode 8 . When the thickness t1 of the ferroelectric layer 2 is 20 μm, the thickness t1 of the ferroelectric layer 2 coincides with twice the total length (w + g: about 10 μm) (2 (w + g)).

  As described above, by configuring the thickness t1 of the ferroelectric layer 2 to be 5 μm or more, a sufficient coverage can be obtained, and the change in the capacitance value according to the displacement of the proof mass 4 is sufficiently large. It was confirmed that it would be possible. As a result, it was confirmed that the power generation capacity can be improved.

In the first embodiment, as described above, the first electrode 7 and the second electrode 8 are formed on the ferroelectric layer 2 side of the proof mass 4, so that the first electrode 7 and the second electrode 8 are interposed. A fringe electric field 10 can be generated. Further, by forming the ferroelectric layer 2 made of BaTiO _{3 in} a predetermined region on the ceramic substrate 1, BaTiO ₃ is a metal oxide (ferroelectric material) having a relative dielectric constant of 1,000 or more. The relative dielectric constant of the ferroelectric layer 2 can be made sufficiently large. For this reason, since the change in the capacitance value caused by the change in the volume ratio of the ferroelectric layer 2 in the fringe electric field 10 can be increased, the vibration applied to the power generation device 50 is converted into a current with high efficiency. be able to.

Further, in the first embodiment, even when the distance d between the ferroelectric layer 2 and the proof mass 4 is increased by forming the ferroelectric layer 2 from BaTiO ₃ , the amount of change in the capacitance value is increased. Therefore, the occurrence of stiction can be suppressed by increasing the distance d between the ferroelectric layer 2 and the proof mass 4. Thereby, the fall of the reliability resulting from generation | occurrence | production of stiction can be suppressed. Since BaTiO ₃ is a ferroelectric substance that does not contain Pb (lead), the ferroelectric layer 2 is made of BaTiO ₃ , thereby reducing the environmental burden caused by waste and giving it to the human body. Adverse effects can be reduced.

In the first embodiment, since the ceramic substrate 1 made of Al ₂ O ₃ is used as the substrate, the insulation and mechanical strength can be improved compared to the case where a silicon substrate or the like is used as the substrate. The power generation capacity can be improved while improving the manufacturing efficiency, and the reliability can be improved. Further, by using the ceramic substrate 1 as the substrate, the manufacturing cost can be reduced as compared with the case where the silicon substrate is used. Furthermore, the MEMS power generation device can be directly formed on the final ceramic package.

  Further, in the first embodiment, by configuring the thickness t1 of the ferroelectric layer 2 to be 5 μm or more, a coverage of 99% or more can be obtained, so that the change in capacitance value can be increased. . Thereby, the power generation capacity can be improved more easily while improving the production efficiency. Note that the thickness t1 of the ferroelectric layer 2 is preferably 10 μm or more, and more preferably 20 μm or more.

In the first embodiment, the smoothness of the upper surface of the ferroelectric layer 2 can be improved by forming the glaze layer 5 between the ceramic substrate 1 and the ferroelectric layer 2. By controlling the particle size of ₃ , irregularities of about 0.1 μm to 0.2 μm can be provided on the upper surface of the ferroelectric layer 2.

  20 to 28 are views for explaining a method of manufacturing the power generation device according to the first embodiment of the present invention. Next, a method for manufacturing the power generation device 50 according to the first embodiment of the present invention will be described with reference to FIGS. 11, 15, 16, and 20 to 28. In addition, the electric power generating apparatus 50 by 1st Embodiment is manufactured mainly using a surface micromachining technique.

First, as shown in FIG. 20, the glaze layer 5 is formed on the upper surface of the ceramic substrate 1 having a thickness of about 1 mm and made of Al ₂ O ₃ . The glaze layer 5 is formed, for example, by printing a liquid containing a glass component on the ceramic substrate 1 and then baking it at a predetermined temperature.

  Next, the wiring layer 6 shown in FIG. 11 is formed on the glaze layer 5 using a screen printing method. Thereafter, as shown in FIG. 20, a ferroelectric layer 2 is formed in a predetermined region on the ceramic substrate 1 (glaze layer 5).

Here, in the first embodiment, the ferroelectric layer 2 is formed using a screen printing method. Specifically, after a paste containing BaTiO ₃ is printed in a predetermined region on the glaze layer 5, the ferroelectric layer 2 made of BaTiO ₃ is formed by firing at a firing temperature of about 800 ° C. to 1200 ° C. To do.

In the first embodiment, the ferroelectric layer 2 is formed so that its thickness t1 (see FIG. 16) is 5 μm to 20 μm, and by controlling the grain size of BaTiO ₃ , the ferroelectric layer 2 The upper surface of the layer 2 is formed so as to have irregularities (not shown) of about 0.1 μm to 0.2 μm.

  Subsequently, as shown in FIG. 21, a sacrificial layer 11 made of amorphous silicon is formed on the glaze layer 5 so as to cover the ferroelectric layer 2 by using a plasma CVD method. Here, the sacrificial layer 11 is a layer formed on the assumption that it will be removed in a later step.

Next, as shown in FIG. 22, an elongated groove (slot) 11a is formed in the sacrificial layer 11 by photolithography and dry etching using SF ₆ plasma gas. Thereafter, as shown in FIG. 23, a first parylene layer 12 is deposited on the upper surface of the sacrificial layer 11. At this time, the first parylene layer 12 deposited in the groove portion 11 a serves as an anchor portion for holding the proof mass 4.

Next, as shown in FIG. 24, a predetermined region of the first parylene layer 12 is removed by photolithography and etching using O ₂ plasma gas.

  Thereafter, an aluminum layer is deposited on the sacrificial layer 11 and the first parylene layer 12 by sputtering or vapor deposition, and the deposited aluminum layer is subjected to photolithography and wet etching as shown in FIG. Pattern. Thereby, the comb-shaped first electrode 7 as shown in FIG. 15 is formed, and the pad electrode 7 c electrically connected to the first electrode 7 is formed. In addition, the connection part 7b (refer FIG. 15) which connects the 1st electrode 7 and the pad electrode 7c is simultaneously formed by the above-mentioned patterning of the aluminum layer.

Further, a CYTOP film is formed on the sacrificial layer 11 by spin coating, and is then etched with O ₂ plasma. By such a process, the electret part of the second electrode 8 is formed in a comb shape.

  Thereafter, on the sacrificial layer 11 and the first parylene layer 12 so as to cover the electret portions of the first electrode 7 and the second electrode 8, the pad electrode 7c, and the connection portion 7b (see FIG. 15), a discharge preventing layer is formed. Parylene (not shown in FIG. 25 and FIG. 26, but for details, see E11 in FIG. 8E) is deposited, and on top of this, the base electrode portion of the second electrode 8, and Aluminum as the pad electrode 8c to be connected is sputtered. Note that the connection portion 8b (see FIG. 15) for connecting the base electrode portion of the second electrode 8 and the pad electrode 8c is also formed simultaneously by the above-described patterning of the aluminum layer.

  Next, as shown in FIG. 26, the second parylene layer 13 is deposited so as to cover the base electrode portion of the second electrode 8, the pad electrode 8c, and the connection portion 8b (see FIG. 15). Then, the second parylene layer 13 is patterned into the shape shown in FIG. Thereby, the proof mass 4 (refer FIG. 11) which consists of parylene, the beam part 9 (refer FIG. 11), and the frame part 3 (refer FIG. 11) are formed. At this time, as shown in FIG. 27 and FIG. 28, an opening 3 a for exposing the surface of the pad electrodes 7 c and 8 c is formed in a predetermined region of the frame 3. Note that the first parylene layer 12 and the second parylene layer 13 can be formed (evaporated) at room temperature.

Finally, the proof mass 4 and the ferroelectric layer 2 are separated from each other by removing a predetermined region of the sacrificial layer 11 by dry etching using XeF ₂ gas. Thus, the power generator 50 according to the first embodiment of the present invention shown in FIG. 11 is formed.

In the manufacturing method according to the first embodiment, as described above, the ferroelectric layer 2 made of BaTiO ₃ is formed in a predetermined region on the ceramic substrate 1 by using the screen printing method. Since it can be easily formed in a predetermined region, the manufacturing efficiency can be improved as compared with the case where a plate-like ferroelectric layer is stuck on the substrate. Note that the power generation device 50 according to the first embodiment can be manufactured without using the DRIE process.

Further, in the first embodiment, the ferroelectric layer 2 made of BaTiO ₃ is formed by using a screen printing method, compared with the case where the ferroelectric layer 2 is formed by using a sputtering method or a sol-gel method. Since the thickness t1 of the ferroelectric layer 2 can be easily increased, it is difficult to increase the change in the capacitance value because the thickness t1 of the ferroelectric layer 2 is small. It is possible to suppress the occurrence of the inconvenience. Thereby, the power generation device 50 with high power generation capability can be obtained while improving the manufacturing efficiency.

  In the first embodiment, the wiring layer 6 can be easily formed by forming the wiring layer 6 on the upper surface of the ceramic substrate 1 (the glaze layer 5) using a screen printing method. Also by this, manufacturing efficiency can be improved.

(Second Embodiment)
FIG. 29 is a perspective view showing the structure of the power generation device according to the second embodiment of the present invention. 30 is a cross-sectional view taken along the line α2-α2 of FIG. FIG. 31 is a plan view of the power generator according to the second embodiment of the present invention shown in FIG. 32 to 35 are views for explaining the structure of the power generation device according to the second embodiment of the present invention. First, with reference to FIGS. 29-35, the structure of the electric power generating apparatus 60 by 2nd Embodiment of this invention is demonstrated.

  As shown in FIGS. 29 and 30, the power generation device 60 according to the second embodiment includes a ceramic substrate 1, a ferroelectric layer 22 formed on the ceramic substrate 1, and a ceramic so as to surround the ferroelectric layer 22. A frame body portion 23 formed on the substrate 1 and a proof mass 24 disposed inside the frame body portion 23 are provided. The ferroelectric layer 22 is an example of the “dielectric layer” in the present invention, and the proof mass 24 is an example of the “movable part” in the present invention.

The ceramic substrate 1 is made of Al ₂ O ₃ and has a thickness of about 1 mm. A glaze layer 5 is formed on the upper surface of the ceramic substrate 1 as in the first embodiment. The glaze layer 5 is provided for obtaining a smooth surface suitable for forming the ferroelectric layer 22 and the like. Further, as shown in FIG. 29, a wiring layer 6 formed by screen printing is provided on a predetermined region outside the frame body portion 23 on the upper surface of the ceramic substrate 1 (glaze layer 5). Yes. The wiring layer 6 is made of, for example, Au (gold).

Here, in the second embodiment, the ferroelectric layer 22 is made of BaTiO ₃ (relative dielectric constant: 1,000 or more), as in the first embodiment. Further, as shown in FIGS. 30 and 32, the ferroelectric layer 22 is formed in a predetermined region on the ceramic substrate 1 (the glaze layer 5) by a screen printing method. The ferroelectric layer 22 has a substantially quadrangular shape when seen in a plan view.

  The ferroelectric layer 22 is configured to have a thickness of 5 μm or more. Specifically, the ferroelectric layer 22 is configured to have a thickness t11 (see FIG. 35) of 5 μm to 20 μm.

  In the second embodiment, as shown in FIGS. 30 and 32, a metal layer 40 (floating electrode) made of aluminum (Al) is formed in a predetermined region on the upper surface side of the ferroelectric layer 22. The metal layer 40 has a predetermined pattern and is formed so as not to protrude from the upper surface of the ferroelectric layer 22. Specifically, the metal layer 40 is formed so as to extend in parallel with the comb teeth portions 27a and 28a of the first electrode 27 and the second electrode 28, which will be described later, in plan view. The metal layer 40 is formed so that the upper surface thereof is substantially flush with the upper surface of the ferroelectric layer 22.

  Further, the proof mass 24 is made of parylene (Parylylene resin) and has a thickness t12 (see FIG. 34) of about 5 μm, as shown in FIGS. Further, as shown in FIG. 31, the proof mass 24 is formed in a substantially quadrangular shape (the length of one side is about 1000 μm) when seen in a plan view.

  Moreover, in 2nd Embodiment, as shown in FIG. 33, two electrodes (the 1st electrode 27 and the 2nd electrode 28) adjoin on the back surface side (lower surface side) of the proof mass 24 in the same plane. It is formed as follows. Specifically, the first electrode 27 and the second electrode 28 are each formed in a comb-like shape in plan view, and the comb-tooth portion 27a of the first electrode 27 and the comb of the second electrode 28 are formed. It is comprised so that the tooth part 28a may be arranged by turns. Further, as shown in FIG. 35, the width w1 of the comb tooth portion 27a of the first electrode 27 and the width w1 of the comb tooth portion 28a of the second electrode 28 are each configured to have a length of about 5 μm, A length g1 from the comb tooth portion 27a of the first electrode 27 to the comb tooth portion 28a of the adjacent second electrode 28 is set to about 5 μm. In the power generator 60 according to the second embodiment, as shown in FIG. 33, the first electrode 27 and the second electrode 28 are formed on almost the entire back surface (lower surface) side of the proof mass 24.

  The first electrode 27 corresponds to a counter electrode, and is made of a metal material such as aluminum (see FIGS. 3A to 3C, B4 in FIG. 4, and E10 in FIG. 8D). In addition, the second electrode 28 includes an electret portion (such as a CYTOP film) that holds a predetermined amount of charge semipermanently and a base electrode portion (such as aluminum) that serves as a reference for potential during power generation. (See reference numerals B2 and B3 in FIGS. 3A to 3C and FIG. 4, reference numeral E9 in FIG. 8C, and reference numeral E12 in FIG. 8E).

  The proof mass 24 includes four beam portions 29 that are integrally connected as shown in FIGS. 29 and 31. Two of these four beam portions 29 are arranged on each of two opposing side surfaces of the proof mass 24, and are formed so as to extend in the same direction when seen in a plan view. Further, the end portions of the four beam portions 29 are integrally connected to the frame body portion 23, respectively. Thus, the proof mass 24 is supported above the ferroelectric layer 22 in a state of being disposed so as to face the ferroelectric layer 22 as shown in FIGS. 29 and 30. The distance d1 (see FIGS. 30 and 35) from the upper surface of the ferroelectric layer 22 to the proof mass 24 (first electrode 27 and second electrode 28) is about 1 μm.

  In the second embodiment, as shown in FIG. 34, the beam portion 29 has a thickness t12 of 10 μm or more and a width w11 of about 3 μm. That is, the length in the thickness direction of the beam portion 29 is larger than the length in the width direction so that the beam portion 29 is easily elastically deformed in the arrow X direction parallel to the upper surface (main surface) of the ceramic substrate 1 (see FIG. 29). Is also made up of large. Thus, when acceleration is applied, the proof mass 24 supported by the four beam portions 29 can move in the direction of the arrow X that is horizontal with respect to the upper surface (main surface) of the ceramic substrate 1 due to its inertial force. It becomes.

  In addition, as shown in FIG. 33, the first electrode 27 described above is electrically connected to the pad electrode 27c via the connecting portion 27b. On the other hand, of the second electrode 28 described above, the electret portion that holds a predetermined amount of charge semi-permanently is in an electrically insulated state, and a base electrode portion for taking a potential reference during power generation Is electrically connected to the pad electrode 28c through the connection portion 28b. Note that the pad electrode 27c is an electrode for extracting a current obtained by power generation, and is connected to a load that is a current supply destination when the power generation device 60 is used. On the other hand, the pad electrode 28c is an electrode for taking a potential reference during power generation, and is connected to a predetermined reference potential when the power generation apparatus 60 is used. Although not explicitly shown in the drawing, the power generation device 60 of the present embodiment applies a predetermined amount of electric charge to the electret portion of the second electrode 28 by contact discharge in the manufacturing process (final stage) of the power generation device 60. An electret terminal for injection is provided. The electret terminal is connected to a predetermined contact discharge device (high voltage application device) at the time of the above charge injection, and is opened or grounded when the power generation device 60 is used.

  Further, as shown in FIG. 30, the frame body portion 23 has a larger thickness than the proof mass 24, and holds the proof mass 24 via the beam portion 29 as shown in FIGS. 29 and 31. It has a function to do. The frame part 23 is mainly composed of parylene. Further, an opening 23a for exposing the surfaces of the pad electrodes 27c and 28c is formed in a predetermined region of the frame body portion 23.

  Other configurations of the second embodiment are the same as those of the first embodiment.

  FIG. 36 is a diagram for explaining the operation of the power generation device according to the second embodiment of the present invention. Next, the operation of the power generation device 60 according to the second embodiment of the present invention will be described with reference to FIGS. 33, 35, and 36.

  In the power generator 60 according to the second embodiment, as shown in FIGS. 35 and 36, the fringe electric field 10 (between the electrodes) is provided between the comb teeth 27 a of the first electrode 27 and the comb teeth 28 a of the second electrode 28. An electric field is generated on the side. Here, as shown in FIG. 33, the first electrode 27 and the second electrode 28 that generate the fringe electric field 10 are formed in a comb-teeth shape, and the comb-teeth portions 27a and 28a are alternately arranged. Since they are arranged, the fringe electric field 10 is uniformly generated on almost the entire back surface (lower surface) side of the proof mass 24. On the other hand, the ferroelectric layer 22 facing the proof mass 24 is in a state of being disposed in the generated fringe electric field 10.

  If a vibration in the horizontal direction (X direction) is applied to the power generation device 60 from this state, an inertial force acts on the proof mass 24, so that the proof mass 24 is in the horizontal direction with respect to the upper surface of the ceramic substrate 1. Move in the X direction. Here, in the fringe electric field 10 generated between the first electrode 27 and the second electrode 28, the electric lines of force can penetrate the ferroelectric layer 22, while penetrating the metal layer 40. Therefore, when the proof mass 24 moves in the direction of the arrow X, the appearance of the electric lines of force changes, and the capacitance of the capacitor formed between the two electrodes according to the change of the appearance of the electric lines of force. The value changes. Along with the capacitance change, a predetermined amount of charge is introduced into the first electrode 27 (counter electrode), and this is output as a current.

  Next, in order to confirm the effect of the power generation device 60 according to the second embodiment, a computer simulation was performed using the same method as in the first embodiment. The result is shown in FIG.

  As shown in FIG. 37, it was found that a coverage of 99% or more can be obtained by configuring the thickness t11 of the ferroelectric layer 22 to be 5 μm or more. Further, when the thickness t11 of the ferroelectric layer 22 is configured to be 10 μm or more, a coverage of almost 100% (99.8% or more) is obtained, and when the thickness t11 is configured to be 20 μm or more, the coverage is 100%. Was found to be obtained. When the thickness t11 of the ferroelectric layer 22 is 10 μm, the thickness t11 of the ferroelectric layer 22 is the width w1 of one comb tooth portion 27a (or 28a) of the first electrode 27 and the second electrode 28. (About 5 μm) and the total length (w1 + g1: about 10 μm) of the length g1 (about 5 μm) from the comb tooth portion 27a of the first electrode 27 to the comb tooth portion 28a of the adjacent second electrode 28 . When the thickness t11 of the ferroelectric layer 22 is 20 μm, the thickness t11 of the ferroelectric layer 22 is equal to twice the total length (w1 + g1: about 10 μm) (2 (w1 + g1)).

  As described above, by configuring the thickness t11 of the ferroelectric layer 22 to be 5 μm or more, a sufficient coverage can be obtained, and the change in the capacitance value according to the displacement of the proof mass 24 is sufficiently large. It was confirmed that it would be possible. As a result, it was confirmed that the power generation capacity can be improved.

  In the second embodiment, as described above, the first electrode 27 and the second electrode 28 are formed on the ferroelectric layer 22 side of the proof mass 24, whereby the comb tooth portion 27a and the second electrode of the first electrode 27 are formed. The fringe electric field 10 can be generated between the 28 comb teeth portions 28a. Further, by forming the metal layer 40 with a predetermined pattern in a predetermined region on the upper surface side of the ferroelectric layer 22, the proof mass 24 is moved in the arrow X direction parallel to the upper surface (main surface) of the ceramic substrate 1. Even in this case, the appearance of the electric lines of force in the fringe electric field 10 can be changed. That is, in the fringe electric field 10 generated between the comb teeth 27a of the first electrode 27 and the comb teeth 28a of the second electrode 28, the electric lines of force can penetrate the ferroelectric layer 22. Since the metal layer 40 cannot be penetrated, the metal layer 40 is formed in a predetermined pattern in a predetermined region on the upper surface side of the ferroelectric layer 22, so that when the proof mass 24 moves in the arrow X direction, The appearance of the electric lines of force in the fringe electric field 10 can be changed. As a result, the capacitance value of the capacitor formed between the two electrodes changes in accordance with the change in the appearance of the lines of electric force, so that a predetermined amount of charge is first generated along with the change in the capacitance value. It is introduced into the electrode 27 (counter electrode), and this is output as a current.

  In the second embodiment, even if the metal layer 40 is formed on the upper surface side of the ferroelectric layer 22 by forming the metal layer 40 so as not to protrude from the upper surface of the ferroelectric layer 22, the metal layer Since the subsequent manufacturing process can be performed in the same process as when the semiconductor layer 40 is not formed, the subsequent manufacturing process is complicated due to the metal layer 40 protruding from the upper surface of the ferroelectric layer 22. The inconvenience of becoming can be suppressed. Thereby, manufacturing efficiency can be improved easily.

  In the second embodiment, the proof mass 24 is formed on the upper surface (main surface) of the ceramic substrate 1 (ferroelectric layer 22) by forming the metal layer 40 so as not to protrude from the upper surface of the ferroelectric layer 22. ), The metal layer 40 and the proof mass 24 (first electrode 27, second electrode 28) can be prevented from engaging with each other. Proof mass in the direction of the arrow X parallel to the upper surface (main surface) of the ceramic substrate 1 (ferroelectric layer 22) due to the engagement of the mass 24 (first electrode 27, second electrode 28). The inconvenience that the movement of 24 is prevented can be suppressed. Thereby, the vibration in the direction of the arrow X parallel to the upper surface (main surface) of the ceramic substrate 1 (ferroelectric layer 22) can be easily extracted as a current.

In the second embodiment, since the ferroelectric layer 22 is made of BaTiO ₃ , BaTiO ₃ is a metal oxide (ferroelectric material) having a relative dielectric constant of 1,000 or more. The relative dielectric constant of the layer 22 can be sufficiently increased. As a result, the change in the capacitance value can be easily increased, so that a larger current is extracted from the vibration in the arrow X direction parallel to the upper surface (main surface) of the ceramic substrate 1 (ferroelectric layer 22). be able to. Since BaTiO ₃ is a ferroelectric material that does not contain Pb (lead), the environmental load caused by waste can be reduced by constituting the ferroelectric layer 22 from BaTiO _3, and it can be applied to the human body. The adverse effect given can be reduced.

  In the second embodiment, the ceramic substrate 1 (ferroelectric layer) is formed by configuring the beam portion 29 supporting the proof mass 24 so that the length in the thickness direction is larger than the length in the width direction. 22) Since the movement of the proof mass 24 in the vertical direction (arrow Z direction) can be suppressed with respect to the upper surface (main surface) of 22), it is possible to suppress the vibration energy from being dispersed in the vertical direction. it can. Thereby, it is possible to easily generate power more efficiently from the vibration in the arrow X direction parallel to the upper surface (main surface) of the ceramic substrate 1 (ferroelectric layer 22).

  Further, in the second embodiment, similarly to the first embodiment, by setting the thickness t11 of the ferroelectric layer 22 to 5 μm or more, a coverage ratio of 99% or more can be obtained, so that the capacitance value The change of can be enlarged. Thereby, it is possible to generate power more efficiently from vibration in the direction of arrow X parallel to the upper surface (main surface) of the ceramic substrate 1 (ferroelectric layer 22).

Furthermore, in the second embodiment, the smoothness of the upper surface of the ferroelectric layer 22 can be improved by forming the glaze layer 5 between the ceramic substrate 1 and the ferroelectric layer 22, so that BaTiO3 can be improved. By controlling the particle size of ₃ , irregularities of about 0.1 μm to 0.2 μm can be provided on the upper surface of the ferroelectric layer 22.

  The remaining effects of the second embodiment are similar to those of the aforementioned first embodiment.

  38 to 48 are views for explaining a method of manufacturing the power generation device according to the second embodiment of the present invention. Subsequently, a method for manufacturing the power generation device 60 according to the second embodiment of the present invention will be described with reference to FIGS. 29, 33 to 35 and 38 to 48. In addition, the electric power generating apparatus 60 by 2nd Embodiment is manufactured mainly using a surface micromachining technique.

First, as shown in FIG. 38, the glaze layer 5 is formed on the upper surface of the ceramic substrate 1 having a thickness of about 1 mm and made of Al ₂ O ₃ . The glaze layer 5 is formed, for example, by printing a liquid containing a glass component on the ceramic substrate 1 and then baking it at a predetermined temperature.

  Next, the wiring layer 6 shown in FIG. 29 is formed on the glaze layer 5 using a screen printing method. In addition, since the wiring layer 6 can be easily formed by forming the wiring layer 6 by the screen printing method, it is also possible to improve the manufacturing efficiency.

Thereafter, as shown in FIG. 38, a ferroelectric layer 22 is formed in a predetermined region on the ceramic substrate 1 (glaze layer 5) by using a screen printing method. Specifically, a ferroelectric layer 22 made of BaTiO ₃ is formed by printing a paste containing BaTiO ₃ in a predetermined region on the glaze layer 5 and then firing at a firing temperature of about 800 ° C. to 1200 ° C. To do.

In addition, the ferroelectric layer 22 is formed so that its thickness t11 (see FIG. 35) is 5 μm to 20 μm, and the grain size of the BaTiO ₃ is controlled, so that the upper surface of the ferroelectric layer 22 has a thickness of 0. It is formed so that unevenness (not shown) of about 1 μm to 0.2 μm is generated.

  Subsequently, as shown in FIG. 39, the ferroelectric layer 22 is recessed by etching, and then a metal layer 40 (aluminum) is formed by sputtering or vapor deposition. Further, the surface is ground to form a prescribed ferroelectric and metal stripe surface as shown in FIG. Thereby, the metal layer 40 is configured not to protrude from the upper surface of the ferroelectric layer 22.

  Thereafter, as shown in FIG. 41, a sacrificial layer 31 made of amorphous silicon is formed on the glaze layer 5 so as to cover the ferroelectric layer 22 by plasma CVD. Here, the sacrificial layer 31 is a layer formed on the assumption that it will be removed in a later step.

Next, as shown in FIG. 42, elongated grooves (slots) 31a are formed in the sacrificial layer 31 by photolithography and dry etching using SF ₆ plasma gas. Then, as shown in FIG. 43, a first parylene layer 32 is deposited on the upper surface of the sacrificial layer 31. At this time, the first parylene layer 32 deposited in the groove portion 31 a becomes an anchor portion for holding the proof mass 24.

Next, as shown in FIG. 44, a predetermined region of the first parylene layer 32 is removed by photolithography and etching using O ₂ plasma gas.

  Thereafter, an aluminum layer is deposited on the sacrificial layer 31 and the first parylene layer 32 by sputtering or vapor deposition, and the deposited aluminum layer is subjected to photolithography and wet etching as shown in FIG. Pattern. Thus, the comb-shaped first electrode 27 as shown in FIG. 33 is formed, and the pad electrode 27c electrically connected to the first electrode 27 is formed. Note that the connecting portion 27b (see FIG. 33) that connects the first electrode 27 and the pad electrode 27c is also formed simultaneously by the patterning of the aluminum layer described above.

In addition, a CYTOP film is formed on the sacrificial layer 31 by spin coating, and is then etched with O ₂ plasma. Through such a process, the electret portion of the second electrode 28 is formed in a comb shape.

  After that, on the sacrificial layer 31 and the first parylene layer 32 so as to cover the electret portions of the first electrode 27 and the second electrode 28, the pad electrode 27c, and the connecting portion 27b (see FIG. 33) Parylene (not shown in FIG. 45 and FIG. 46, but for details, see E11 in FIG. 8E) is deposited, and on top of this, the base electrode portion of the second electrode 28, and Aluminum as the pad electrode 28c to be connected is sputtered. Note that the connection portion 28b (see FIG. 33) that connects the base electrode portion of the second electrode 28 and the pad electrode 28c is also formed simultaneously by the above-described patterning of the aluminum layer.

  Next, as shown in FIG. 46, the second parylene layer 33 is deposited so as to cover the base electrode portion of the second electrode 28, the pad electrode 28c (see FIG. 33), and the connection portion 28b (see FIG. 33). Then, the second parylene layer 33 is patterned into the shape shown in FIG. At this time, as shown in FIG. 34, each of the four beam portions 29 is formed so that the length in the thickness direction is larger than the length in the width direction. Thereby, the proof mass 24 (refer FIG. 29) which consists of parylene, the beam part 29 (refer FIG. 29), and the frame part 23 (refer FIG. 29) are formed. At this time, an opening 23 a for exposing the surfaces of the pad electrodes 27 c and 28 c is formed in a predetermined region of the frame body portion 23. Note that the first parylene layer 32 and the second parylene layer 33 can be formed (evaporated) at room temperature.

Finally, the proof mass 24 and the ferroelectric layer 22 are separated from each other by removing a predetermined region of the sacrificial layer 31 from the state shown in FIG. 48 by dry etching using XeF ₂ gas. In this way, the power generation device 60 according to the second embodiment of the present invention shown in FIG. 29 is formed.

  In the second embodiment, as described above, the ferroelectric layer 22 is formed in the predetermined region on the ceramic substrate 1 by forming the ferroelectric layer 22 in the predetermined region on the ceramic substrate 1 using the screen printing method. Therefore, the manufacturing efficiency can be improved as compared with the case where the plate-like ferroelectric layer 22 is attached to a predetermined region on the ceramic substrate 1. In addition, in the electric power generating apparatus 60 by 2nd Embodiment, it can manufacture without using a DRIE process.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

For example, in the first and second embodiments, the ferroelectric layer is made of BaTiO _3. However, the present invention is not limited to this, and the relative permittivity is 1,000 or more, and screen printing is performed. As long as the method is applicable to the metal oxide, the ferroelectric layer may be made of a metal oxide other than BaTiO ₃ . At this time, it is preferable to use a metal oxide not containing Pb (lead).

  In the first and second embodiments, the ferroelectric layer is configured to have a thickness of 5 μm to 20 μm. However, the present invention is not limited to this, and the ferroelectric layer is configured to have a thickness of 20 μm or more. May be. Since the ferroelectric layer is formed by the screen printing method as described above, a ferroelectric layer having a thickness of 20 μm or more can be easily formed.

  In the first and second embodiments, the example in which the ferroelectric layer is formed on the ceramic substrate on which the glaze layer is formed using the screen printing method has been described. However, the present invention is not limited to this. The ferroelectric layer may be formed on the ceramic substrate on which the glaze layer is not formed by using a screen printing method.

  Further, in the first and second embodiments, the example in which the ferroelectric layer is formed by firing at a firing temperature of about 800 ° C. to 1200 ° C. is shown, but the present invention is not limited to this and is described above. The ferroelectric layer may be formed by firing at a firing temperature other than the firing temperature. For example, it may be fired at a relatively high firing temperature of about 1200 ° C. to 1500 ° C., or may be fired at a relatively low firing temperature of 700 ° C. or less. When firing at a firing temperature of about 1200 ° C. to 1500 ° C., a ferroelectric layer is formed on a ceramic substrate on which no glaze layer is formed, and a wiring layer is formed after the ferroelectric layer is formed. Then, the power generation device shown in the above embodiment can be manufactured. Further, when firing at a firing temperature of 700 ° C. or lower, it is preferable that the relative dielectric constant of the ferroelectric layer is not 1,000 or lower.

In the first and second embodiments, the example using the ceramic substrate made of Al ₂ O ₃ has been shown. However, the present invention is not limited to this, and the ceramic substrate made of a ceramic material other than Al ₂ O ₃ is used. In addition to the use, a power generation device may be manufactured using a ferroelectric material as a substrate.

  In the first and second embodiments, the proof mass is held by the frame body portion. However, the present invention is not limited to this, and the proof mass is held by a member other than the frame body portion. May be.

  In the first and second embodiments, the proof mass may be provided with a plurality of through holes penetrating from the upper surface to the lower surface. When configured in this manner, the sacrificial layer can be easily removed and the air resistance can be reduced.

  In the second embodiment, the example in which the metal layer is formed so as not to protrude from the upper surface of the ferroelectric layer has been described. However, the present invention is not limited thereto, and the metal layer is formed on the upper surface of the ferroelectric layer. You may form so that it may protrude from.

  Moreover, although the said 2nd Embodiment demonstrated the example which comprised the metal layer from aluminum, this invention is not restricted to this, You may comprise a metal layer from metals other than aluminum.

(First modification)
In the second embodiment, the proof mass is supported by the four beam portions. However, the present invention is not limited to this, and the proof mass is moved in a predetermined direction parallel to the upper surface of the ceramic substrate. If possible, the configuration of the beam portion supporting the proof mass may be a configuration other than the configuration according to the above embodiment. For example, as shown in FIG. 49, the beam portion 39 that supports the proof mass 34 may be configured to bend in the arrow X direction.

(Second modification)
Further, in the second embodiment, the example in which the power generation device is configured to be able to generate power from the vibration in the arrow X direction parallel to the upper surface of the ceramic substrate has been described. However, the present invention is not limited to this, and one ceramic is provided. A plurality of power generation devices may be formed on the substrate so that power can be generated simultaneously from vibrations in a plurality of directions. For example, as shown in FIG. 50, at least two power generation devices 60 that generate power from vibrations in the directions of arrows X and Y parallel to the upper surface of the ceramic substrate 1 and perpendicular to the upper surface of the ceramic substrate 1. The power generation device 50 that generates power from vibrations in the direction may be formed on one ceramic substrate 1 so that power can be generated simultaneously from vibrations in the three axial directions.

(Third Modification)
Next, a third modification of the power generation device described above (particularly the power generation device of the second embodiment that generates power from horizontal vibration) will be described in detail. 51A and 51B are both cross-sectional views showing the structure of the power generation device according to the third modification of the present invention. 51A, the metal layer (floating electrode) G2 is formed so as to protrude on the surface of the ferroelectric substrate G1, as in FIGS. 3A to 3C. In the power generator of FIG. Similar to 30, a metal layer G2 is formed to be buried on the surface of the ferroelectric substrate G1.

Here, the power generation device of the third modified example includes a protective layer G3 that covers the ferroelectric substrate G1 and the metal layer G2 and has a surface horizontal to the movable body G4. The material of the protective layer G3 is a fluororesin or polyimide resin having a small friction coefficient and excellent insulation (for example, a static friction coefficient of 0.5 or less and a relative dielectric constant of 4.0 or less). Is preferred. Note that the relative dielectric constant of an interlayer insulating film generally used in the field of semiconductor devices is 4.0 or less. For example, the relative dielectric constant of SiO ₂ is 4.0. As the material of the protective layer G3, the smaller the relative dielectric constant, the better. However, in view of the availability of the material, an interlayer insulating film material generally used in the field of semiconductor devices may be used.

  For example, in the configuration having the protective layer G3 having a small friction coefficient, even when the ferroelectric substrate G1 and the movable body G4 are in contact with each other, the movable body G4 smoothly moves on the surface of the protective layer G3. Since it slides, it becomes possible to avoid mechanical destruction of the power generator. Moreover, if it is the structure which has the protective layer G3 excellent in insulation, it will become difficult to produce unnecessary discharge between the metal layer (floating electrode) G2, and the counter electrode G5 and the electret electrode G6.

  In particular, in the power generation device in which the distance between the gaps between the ferroelectric substrate G1 and the movable body G4 is short, the above contact and discharge problems are likely to occur. Therefore, it is desirable to employ the configuration of the third modification.

  Note that the metal layer G2 in FIG. 51B is formed so that its upper surface is substantially flush with the upper surface of the ferroelectric substrate G1.

  As a formation method thereof, a groove (trench) is formed on the surface of the ferroelectric substrate G1, and then a metal layer G2 is stacked therein, as in a fourth modification described later. At this time, the depth of the groove may be appropriately designed so that the metal layer G2 has a necessary and sufficient thickness to block the fringe electric field. Note that a semiconductor layer (such as a pure silicon layer) may be stacked in the groove instead of the metal layer G2 as long as the fringe electric field can be appropriately blocked.

  51B (that is, a configuration in which the metal layer G2 is buried on the surface of the ferroelectric substrate G1), the configuration of FIG. 51A (that is, the metal layer G2 is projected on the surface of the ferroelectric substrate G1). The distance between the gaps of the ferroelectric substrate G1 and the movable body G4 can be shortened by the thickness of the metal layer G2, compared with the configuration), which contributes to reducing the size of the power generation device and improving the power generation efficiency. It becomes possible to do.

(Fourth modification)
Next, a fourth modification of the power generation apparatus described above (particularly the power generation apparatus of the second embodiment that generates power from horizontal vibration) will be described in detail. 52A and 52B are schematic diagrams for explaining the power generation principle of the power generation device according to the fourth modification of the present invention. 52A shows a state where the movable body H1 exists at the initial position, and FIG. 52B shows a state after the movable body H1 is horizontally moved. Further, on the left side of FIGS. 52A and 52B, equivalent circuits schematically showing the concept and operating principle of the power generation device are depicted, respectively.

  In the power generator of the fourth modification, a groove (trench) H6 is formed on the surface of the ferroelectric substrate H5 instead of the metal layer. The groove portion (trench portion) H6 may be formed by wet etching, dry etching using an ICP apparatus, machining (dicing), laser beam processing using an excimer laser, or the like. In order to further stack a structure such as the movable body H1 on the upper portion of the ferroelectric substrate H5 in which the groove portion (trench portion) H6 is formed, as shown in FIG. A sacrificial layer made of amorphous silicon is formed so as to cover the ferroelectric substrate H5, a new horizontal plane is obtained, a desired structure is laminated on the upper part, and the sacrificial layer is finally removed. Good.

  The depth of the trench (trench) H6 may be designed to be equal to or greater than the gap length (= about 1 μm) between the movable body H1 and the ferroelectric substrate H5. Further, it is desirable that the width or pitch of the groove (trench) H6 is appropriately designed in consideration of the relationship with the width or pitch of the electret H2 and the counter electrode H4. Further, it is desirable that the taper shape of the groove (trench) H6 is appropriately designed in consideration of the machining process.

The operation principle of the power generation device having the above configuration will be described. When the movable body H1 is moved in the horizontal direction by an external vibration input, the relative relationship between the fringe electric field H7 and the groove portion (trench portion) H6 is shown in comparison with FIGS. 52A and 52B. The arrangement relationship changes, and the state of the lines of electric force passing through the ferroelectric substrate H5 changes. For example, at the initial position of the movable body H1 (see FIG. 52A), there is a convex portion of the ferroelectric substrate H5 between the electret H2 and the counter electrode H4, and the gap length between the movable body H1 and the ferroelectric substrate H5. Is relatively short, that is, the electric lines of force are likely to enter the ferroelectric substrate H5, but in the position after the horizontal movement of the movable body H1 (see FIG. 52B), the electret A groove portion (trench portion) H6 exists between H2 and the counter electrode H4, and the gap length between the movable body H1 and the ferroelectric substrate H5 is relatively long, that is, the electric lines of force are the ferroelectric substrate. It becomes difficult to enter the inside of H5. This fact means that the capacitance C formed between the electret H2 and the counter electrode H4 changes. The change in the capacitance C is caused by a change in the volume ratio between the dielectric and air existing between the two electrodes, that is, the equivalent relative dielectric constant ε _r . Along with the change in capacitance between the two electrodes, a predetermined amount of charge Q is introduced into the counter electrode H4. The electric charge Q is drawn out as a current I based on the above-described equation (2).

  As described above, the power generation device according to the fourth modification can generate power based on horizontal vibration without providing a metal layer on the surface of the ferroelectric substrate H5. It is possible to prevent electrical discharge, and consequently, it is possible to reduce the distance between the gaps between the ferroelectric substrate H5 and the movable body H1, thereby contributing to downsizing of the power generation device and improvement of power generation efficiency. Become.

  53A to 53C are cross-sectional views showing first to third structural examples of the power generating device according to the fourth modified example of the present invention, respectively. FIG. 53A shows a first structure example (trench formation type), FIG. 53B shows a second structure example (silica laminated type), and FIG. 53C shows a third structure example (protection layer formation). Type).

The first structure example (trench formation type) in FIG. 53A is the structure already shown in FIGS. 52A and 52B. On the surface of the ferroelectric substrate I2, wet etching, dry etching using an ICP apparatus, etc. A groove portion (trench portion) I3 is formed by machining (dicing), laser beam processing using an excimer laser or the like, and the inside thereof is a low vacuum as in the gap region between the movable body I1 and the ferroelectric substrate I2. Is in a state (not a high vacuum or ultra-high vacuum), or air, an inert gas (N ₂ or the like), or a gas having an anti-discharge effect (for example, a gas containing SF ₆ as a main component), etc. Is filled. With such a configuration, the gap region and the state (dielectric constant) inside the trench can be matched. The reason why the gap region and the inside of the trench are not made high vacuum or ultra high vacuum is to avoid discharge. In this specification, “low vacuum state” refers to a state of atmospheric pressure to 10 ⁻¹ Pa, “high vacuum state” refers to a state of 10 ⁻¹ to 10 ⁻⁵ Pa, “Vacuum state” refers to a state of 10 ⁻⁵ or less.

  The second structural example (silica laminated type) in FIG. 53B is formed by laminating a silica layer I3 ′ (dielectric constant of about 3) inside the groove (trench portion) I3 formed in the first structural example in FIG. 53A. The surface of the body substrate I2 is flattened. With such a configuration, it is possible to reduce contact (hook) between the movable body I1 and the ferroelectric substrate I2. Further, by flattening the surface of the ferroelectric substrate I2, a structure can be formed on the ferroelectric substrate I2 by surface micromachining.

  The third structure example (protective layer forming type) in FIG. 53B covers the ferroelectric substrate I2 and the silica layer I3 ′ in addition to the second structure example in FIG. 53B, and is a surface horizontal to the movable body I1. This is a structure in which a protective layer I4 having the following is added. In addition, as a raw material of the protective layer I4, a fluororesin with a small friction coefficient etc. is suitable. With this configuration, even when the ferroelectric substrate I2 and the movable body I1 are in contact with each other, the movable body J1 slides smoothly on the surface of the protective layer J4. It is possible to avoid mechanical destruction.

  It should be noted that the configuration of the present invention can be variously modified within the scope of the gist of the invention in addition to the above-described embodiment or modification. That is, the above-described embodiment is an example in all respects and should not be considered as limiting, and the technical scope of the present invention is not the description of the above-described embodiment, but the claims. It should be understood that all modifications that come within the meaning and range of equivalents of the claims are included.

For example, the gap between the ferroelectric substrate and the movable body may be in a low vacuum state, or air, an inert gas (such as N ₂ ), or a gas having an anti-discharge effect (SF ₆ as a main component). Or the like). In addition, when making the said gap into a low vacuum state, you may use a deaeration process, or you may utilize the phenomenon which gas will escape from said gap at the time of some high temperature processes, and will be in a low vacuum state naturally. .

  As for the ferroelectric provided at the position facing the movable body, the substrate itself may be formed of a ferroelectric material (see FIG. 3A to FIG. 3C, for example), or thin film printing technology is used on the substrate. A ferroelectric layer may be formed (see FIGS. 8A to 8F), or a plate-like ferroelectric formed in a separate process may be attached to the substrate (see FIG. 8A to FIG. 8F). (See FIGS. 14 and 32).

  The power generator according to the present invention is a technology that can be suitably used as a power source for various sensors and wireless devices, for example.

A1 Base electrode A2 Electret A3 Parylene A4 PZT plate A5 Counter electrode B1 Proof mass (movable body)
B2 electret B3 Base electrode B4 Counter electrode B5 Ferroelectric substrate B6 Floating electrode B7 Fringe electric field B8 Air C1 Power generator (for X direction)
C2 power generator (for Y direction)
C3 power generator (for Z direction)
D1 proof mass (movable body)
D2 Beam part D3 Electret D4 Counter electrode D5 Floating electrode E1 Silicon wafer E2 Adhesive (PDMS)
E3 PZT plate (ferroelectric substrate)
E4 Aluminum (floating electrode)
E5 Amorphous silicon (sacrificial layer)
E6 slot (groove)
E7 dimple
E8 Parylene E9 CYTOP film (electret)
E10 Aluminum (counter electrode)
E11 Parylene E12 Aluminum (base electrode)
E13 Parylene E14 SU-8 layer F1 Silicon wafer F2 Parylene F3 CYTOP film F4 Discharge simulator F5 Switch G1 Ferroelectric substrate G2 Metal layer (floating electrode)
G3 Protective layer G4 Movable body G5 Counter electrode G6 Electret electrode H1 Movable body H2 Electret H3 Base electrode H4 Counter electrode H5 Ferroelectric substrate H6 Groove (trench)
H7 Fringe field I1 Movable body I2 Ferroelectric substrate I3 Groove (trench)
I3 'Silica layer I4 Protective layer 1 Ceramic substrate 2, 22 Ferroelectric layer (dielectric layer)
3, 23 Frame part 3a, 23a Opening part 4, 24 Proof mass (movable part)
5 Glaze layer 6 Wiring layer 7, 27 First electrode (counter electrode)
7a, 27a Comb teeth portion 7b, 27b Connection portion 7c, 27c Pad electrode 8, 28 Second electrode (electret)
8a, 28a Comb tooth portion 8b, 28b Connection portion 8c, 28c Pad electrode 9, 29 Beam portion 10 Fringe electric field 11, 31 Sacrificial layer 11a, 31a Groove portion (slot)
40 Metal layer (floating electrode)
50 Power generator (for Z direction)
60 Power generator (for X direction / Y direction)

Claims (15)

With dielectrics;
A movable part facing the dielectric at a predetermined distance;
An electret and a counter electrode, each formed on the dielectric side of the movable part, for generating a fringe electric field so as to penetrate the dielectric between the two electrodes;
Comprising
When the volume occupancy ratio of the dielectric occupying between the electret and the counter electrode changes in accordance with the horizontal displacement of the movable body, the charge introduced into the counter electrode is output to the outside of the device as a current. A power generator that
A metal layer formed on the movable part side surface of the dielectric material for preventing the fringe electric field from entering the dielectric material;
A low-dielectric insulating film that is formed so as to cover the dielectric and the metal layer, and that has a surface parallel to the movable body, such as a fluororesin or a polyimide resin;
A power generator characterized by comprising.   The power generation apparatus according to claim 1, wherein the metal layer is formed so as to protrude on the movable portion side surface of the dielectric.   The power generation apparatus according to claim 1, wherein the metal layer is formed so as to be buried on a movable part side surface of the dielectric. With dielectrics;
A movable part facing the dielectric at a predetermined distance;
An electret and a counter electrode, each formed on the dielectric side surface of the movable part, for generating a fringe electric field so as to penetrate the dielectric between the two electrodes;
Comprising
When the volume occupancy ratio of the dielectric occupying between the electret and the counter electrode changes in accordance with the horizontal displacement of the movable body, the charge introduced into the counter electrode is output to the outside of the device as a current. A power generator that
The power generator according to claim 1, wherein the dielectric is formed on a surface of the movable part and has a groove for preventing the fringe electric field from entering the dielectric.   5. The power generator according to claim 4, further comprising a low dielectric constant layer made of silica or the like, which is laminated inside the groove and flattenes the movable part side surface of the dielectric.   A low dielectric insulating film having good slidability, such as fluorine resin or polyimide resin, which is formed so as to cover the dielectric and a low dielectric constant layer such as silica and has a surface parallel to the movable body. The power generator according to claim 5, wherein   The power generator according to any one of claims 1 to 6, wherein the support member of the movable portion includes a beam portion having a length in the thickness direction larger than a length in the width direction.   The electret and the counter electrode are each formed in a comb-teeth shape having a plurality of comb-teeth parts, and the comb-teeth parts are alternately arranged with a predetermined interval in a plan view. The power generation device according to any one of claims 1 to 7, wherein:   The power generator according to any one of claims 1 to 8, further comprising an electret terminal for injecting a predetermined amount of electric charge to the electret by contact discharge.   The power generator according to any one of claims 1 to 9, wherein the dielectric has a relative dielectric constant of 1,000 or more.   The power generation device according to any one of claims 1 to 10, wherein a gap region between the dielectric and the movable body is in a low vacuum state.   The power generation device according to claim 1, wherein a gap region between the dielectric and the movable body is filled with a predetermined gas.   The power generation device according to claim 12, wherein the predetermined gas is any one of air, an inert gas, and a gas having a discharge preventing effect. Generator according to claim 13, wherein the main component of the gas with the discharge preventing effect is SF _6.   The power generation device according to any one of claims 1 to 14, wherein the power generation device is manufactured using a surface micromachining technique.